Perennial ryegrass, lucerne and maize were ensiled for 100 days in polythene-bag silos without additive or after the addition of aorylic acid at 0·125, 0·25 and 0·50% of fresh crop weight, sodium acrylate at 0·165, 0·33 and 0·66% of fresh crop weight and formic and propionic acid at 0·25% of fresh crop weight.

Both acrylic acid and sodium acrylate were effective in restricting fermentation and protein breakdown in the silo. At 0·25% acrylic acid and the corresponding rate of sodium acrylate (0·33%) they were more effective in restricting fermentation than formic or propionic acids at 0·25%. At all rates of application they were effective in preventing deterioration of maize silage exposed to air for 13 days but not with ryegrass. Lucerne silages made both with and without additives were stable when exposed to air.

It is suggested that because of its non-volatility and non-corrosive properties sodium acrylate has advantages over the additives at present available.

Screening methods were devised to select cowpea genotypes with resistance to yield loss oaused by larvae of Maruca testulalis (Lepidoptera, Pyralidae). More emphasis was placed on flower damage than on pod damage. One hundred and forty genotypes of wild and cultivated cowpeas and four of related Vigna speoies were screened in the first year; 25 of these were selected for rescreening in the second year. Resistance to flower damage was assessed by the ratio of number of pods under unsprayed conditions to number of pods under sprayed conditions and resistance to overall post-flowering damage by ratio of seed yield under unsprayed conditions to seed yield under sprayed conditions. The absolute numbers of pods and seed yields from unsprayed plots were also taken into account. Several genotypes of moderate resistance and one of high resistance were located among cultivars of different origins.

It is suggested that the empirical approach to the search for insect resistance, particularly the comparison of unprotected with protected yields, has great potential, especially for seriously damaged crops.

The birthcoat of coarse wool Barki lambs was investigated at the age of 1–1·5 months. Lambs were covered when they were 2 months old to study kemp succession, and some other adult fleece traits, at the age of 16 months in relation to the birthcoat fibre type arrays. Samples were taken from three dorsal and three lateral positions. The average halo hair grade was 5·45% and the coarse fibre type array, plateau, contributed 64·7% of the birthcoat arrays, the rest were of the less coarse, saddle, type. Halo hair grade and fibre type arrays showed an antero-posterior gradient, increasing in score and coarseness posteriorly.

All halo hairs, 41·9% of super sickles and 22·6% of hairy tip curly tip fibres were shed as first generation kemp (G1 Curly tip and histerotrich fibres shed the least and they contributed the majority of the total persistent fibres. When pre-curly tip fibres increased in the birthcoat samples, that was followed by more kemp in the adult fleece.

The average G1% kemp was 4·43. Kemp decreased in subsequent generations, values were 34·50 and 8·37 for G2/G1% and G1/%, respectively. G1%, and G2/G1% kemp showed a general trend of an increase towards posterior positions; the shoulder position was an exception to that.

Coarse birthcoat fibre type arrays, plateau, were followed by more kemp in G1% and in successive generations than were the less coarse, saddle, arrays. High values of G2/G1% kemp were followed by significantly high G3/G1% kemp. Within animals, there was a significant correlation (P < 0·01) between halo hair grade and G1% kemp.

Staple length showed a tendency to increase towards posterior positions and females showed slightly longer staples than those of males. A slight trend of decrease in staple length was observed following the less coarse array, saddle, as compared with that which followed the coarse array, plateau.

For selection against kemp at an early stage, though birthcoat halo hair grade was positively correlated with G1% kemp, a high halo hair grade is essential for the lamb's early survival, hence fibre type arrays should be considered in selection. Less coarse birthcoat arrays, saddle in the present material, and a high, within array, curly tip: pre-curly tip ratio would be preferrable.

Five strains of Rhizobium sp. were studied in vivo for their nodulation capacity, leghaemoglobin content of nodules, crude protein and four amino acids content in five genotypes of chick pea in calcareous soil. Inoculation with Rhizobium led to a significant increase in grain yield compared with the uninoculated control. Genotype C 235 gave significantly higher grain yield than the others. The interactions between strains and genotypes were significant. Genotype C 235 gave maximum grain yield (2·2 t/ha) when treated with strain KG 41. Genotype C 235 exhibited maximum leghaemoglobin content and amino acids.

The effect of the amount of milk consumed upon the herbage intake and performance of calves at pasture, following a standard rearing period, was investigated using 50 Hereford × Friesian calves purchased at 10–12 days ofage. All calves were offered 6 kg reconstituted milk substitute for a 58 day period indoors and for a subsequent 31 days at pasture. Ten calves were then allocated to each of five milk treatments (0, 2, 4, 6, 10 kg/day) and grazed for a further 63 days. The calves were offered a daily herbage allowance of 60 g dry matter/kg live weight.

Daily weight gain was increased by 59 g for each additional kilogramme of reconstituted milk consumed, and herbage intake per unit live weight decreased by 1–24 g/g milk organic matter consumed, equivalent to a reduction in metabolizable energy intake of 9 kJ. Clear effects of both age and diet upon the consumption of herbage were demonstrated. An explanation of the mechanisms governing intake of herbage in milk–fed calves is offered.

A total of 146 nulliparous gilts at two centres were assigned to lactation lengths of 10, 25 or 40 days and maintained on the same weaning regime for up to five parities.

The interval between weaning and conception tended to be shorter for the 40-day treatment with little difference between the 10- and 25-day treatments. The data from all parities were pooled on the basis of an assumed herd structure giving the number of litters produced per sow per year aa 2·63, 2·37 and 2·18 for the 10-, 25- and 40-day treatments respectively.

The number of pigs born alive per litter remained more or less static with successive parities on the 10-day treatment but increased on the 40-day treatment with differences between treatment s reaching or approaching significance in parities 4 and 5. Although this trend was reflected in the number of pigs weane d per litter, the differences between lactation treatments were non-significant as a result of higher post-natal mortality in the larger litters of the longer lactating sows.

Consequently sows on the 10-day treatment reared the highest number of pigs per year, 22·4 compared with 20·2 and 19·8 for 25- and 40-day lactations respectively.

Data are also presented on changes in sow live weight.

A high culling rate and an extended interval betwee n weaning and conception were experienced at one centre in parity 1. The possible reasons and effect on subsequent litter size are discussed.

Two field experiments were conducted at Aberystwyth on simulated swards of S. 23 perennial ryegrass which were cut one or more times between August and January. The further effect of cutting in early spring was also examined.

The weight of harvestable herbage produced in spring was found to be much less from plots which had been cut frequently in autumn and winter, and was also reduced when the final cutting date was progressively delayed.

The principal effect of later and more frequent cutting in autumn on developmental morphology was a dramatic reduction in the length of leaves produced subsequently. This effect persisted well into the spring period. Numbers of tillers and leaves were much less affected. Thus a greater bulk of herbage was present in spring on autumnrested swards. Production of new tillers in spring was, however, encouraged by greater levels of prior utilization, including cutting in March.

Total herbage yields from the different defoliation systems up to and including different harvesting dates in spring were very similar, but contained a higher percentage of dead material when autumn growth had been allowed to accumulate for longer periods. Under these systems considerable numbers of leaves were formed but died without being harvested. Tiller survival at low temperatures was poorer in swards left undefoliated after the end of August.

Results from two trials, in which the effects of genotype, plant density and harvest date on the accumulation of dry matter and the chemical composition and nutritive value of plant components, are presented. Inra 200, LG11, Maris Saffron, Caldera 535, Anjou 210 and White Horse Tooth were established at 5·0, 9·8 and 13·5 plants/m2 in factorially designed experiments.

In vitro digestible organic matter in the dry matter, water-soluble carbohydrates, starch, total nitrogen, acid-detergent fibre, cellulose, lignin, phosphorus, magnesium, potassium, calcium, sodium, zinc, manganese and copper were analysed for the whole crop and plant components.

With the exception of White Horse Tooth, stem yields declined after reaching a peak 2–3 weeks after mid-silk. This was attributed to movement of water-soluble carbohydrates from the stem to the ear, with greater movement being associated with a larger ear component. As a result the in vitro digestible organic matter in the dry matter value of the stem component was greater for crops containing a small proportion of ear. The higher stem digestibility value compensated for the small ear component, with the result that the varying proportions of plant components did not markedly affect whole-crop digestibility prior to ensiling.

The greater deposition of starch in crops with a large ear component caused a significantly more rapid rise in whole-crop D.M. content than in crops with a small ear component.

Acid-detergent fibre and lignin values for the whole crop were much lower than those recorded in the U.S.A. Genotype and plant density had no effect on mineral content but phosphorus and potassium concentrations declined dramatically after frost.

Forage maize was harvested on three occasions from three genotypes (Inra 200, LG11 and Anjou 210), grown at three plant densities (5·0, 9·8 and 13·5 plants/m2). Three replicate silos were filled with 8 kg fresh crop per treatment, sealed, and stored for 100 days.

Crops from all treatments fermented to give predominantly lactic acid, low values for pH (average 3·9, range 3·7–4·1), with no butyric acid. Apparent loss of watersoluble carbohydrates during storage appeared to be directly related to their content at harvest.

Genotype and plant density had relatively little effect on the composition of the silage, or on digestibility in vitro. Later harvest was reflected in increased contents of dry matter and starch, and in restricted fermentation. The content of digestible organic matter in the D.M. was decreased by later harvest.

Maize (Anjou 210), a density-sensitive genotype, was established at 5 and 15 plants/m2 and produced crops containing 50 and 26% grain respectively. Prior to ensiling, the high and low grain crops contained 6·9 and 20·4% water-soluble carbohydrates in the dry matter respectively and were reduced to 0·4 and 1·6% of the dry matter in the silage. The high grain silage contained a lower concentration of acid-detergent fibre, cellulose, lignin, cell-wall constituents and organic acids than the low grain silage. These differences were not reflected in the in vitro digestible organic matter in the dry matter values which were similar in both silages.

Two groups of autumn-calving Freisian cows were offered either the high or low grain silage ad libitum as the sole forage plus an 18% crude protein concentrate during a 14-week experimental period. The cows which received the high grain silage produced significantly more milk of a significantly lower milk fat content than the cows which received the low grain silage.

The increased milk production coupled with the smaller loss of water-soluble carbohydrates during ensiling show that a high grain content in forage maize is a desirable attribute. It is suggested that density tolerance should be one of the selection criteria used by plant breeders to allow crops to be established at high plant densities from which near maximum dry-matter yields could be obtained, while still containing a high proportion of grain.

A method is proposed for estimating the percentage of dietary protein that is degraded by microbial action in the rumen when protein supplement is added to a specified ration. The potential degradability, p, is measured by incubating the supplement in artificial-fibre bags in the rumen and is related to incubation time, t, by the equation p = a+b(1 – e-ct). The rate constant k, measuring the passage of the supplement from the rumen to the abomasum, is obtained in a separate experiment in which the supplement is combined with a chromium marker which renders it completely indigestible. The effective percentage degradation, p, of the supplement, allowing for rate of passage, is shown to be p = a+[bc/(c+k)] (1-e-(e+k)t) by time, t, after feeding. As t increases, this tends to the asymptotic value a+bc/(c+k), which therefore provides an estimate of the degradability of the protein supplement under the specified feeding conditions.

The method is illustrated by results obtained with soya-bean meal fed as a supplement to a dried-grass diet for sheep. The incubation measurements showed that 89% of the soya-bean protein disappeared within 24 h and indicated that it was all ultimately degradable with this diet.

When the dried grass was given at a restricted level of feeding the allowance for time of retention in the rumen reduced the estimate of final degradability to 71% (69% within 24 h). With ad libitum feeding there was a faster rate of passage and the final degradability was estimated to be 66% (65% within 24 h).

The incidence of oestrus in pregnant ewes has been reported previously by Williams et al. (1956) and Bichard et al. (1974). However, their investigations were not designed specifically to study such a phenomenon and the number of animals employed was small. None of the factors affecting oestrus occurrence was investigated. Under experimental conditions, vasectomized or aproned rams are sometimes used after the removal of fertile rams to detect embryonic failure in pregnant ewes. It is of interest to check on the validity of this method. This study was carried out to obtain an estimate of the incidence of oestrus in early pregnancy using relatively large numbers of fat-tailed Barki and imported Hungarian Merino ewes and to investigate the effect of year, breed of ewe and age of ewe on its occurrence.

The numbers of viable anaerobic proteolytic bacteria were determined from the caecal fluid of three ponies fed diets based on maize, oats or barley. In anaerobic conditions selected to promote the growth of those bacteria capable of utilizing protein, between 2 × 105 and 8 × 105 of viable anaerobic proteolytic bacteria/ml of caeoal fluid were observed. Time of sampling post feeding did not appear to affect the numbers observed. These numbers would appear adequate to make an important contribution to protein digestion.

Although sheep combat thermal stress mainly by panting, a sizeable amount (40%) of total evaporative heat loss, is from sources other than panting (Hales & Brown, 1974). The frequency of sporadic discharge of sweat glands increases with increase in ambient temperature and is accompanied by a decline in respiration rate (Bligh, 1961). The wool coat can reduce evaporative cooling but sweating may have cooling value in sheep breeds with open fleeces (Rai, Singh & More, 1978). In sheep, the number and size of the sweat glands (Waites & Voglmayr, 1962) and the quantum of sweat production in a particular time period (Ghoshal et al. 1977) varies in different body regions. In view of the possible significance of surface evaporative cooling, thermal sweating in different body regions of sheep was investigated.